In particular, nowadays it is particularly desirable that a motor vehicle also offers a so-called remote service, in which the motor vehicle can be controlled from outside, for example, via the Internet. As service routine, it must thus be ensured that the motor vehicle responds to control commands from outside. For such remote services, control units nowadays often remain permanently logged in, for example, in a cellphone network, and wait for incoming SMS messages (SMS—Short Message Service) or an incoming call. In order to be able to offer this function in a parked motor vehicle for a duration of several months, a very large battery has to be built in.
On this topic, it is known from WO 2006/119976 A1 to receive a wake-up signal by means of a vehicle-side receiver of a radio remote control, wherein at least one wireless communication module of the motor vehicle is woken up by the wake-up signal. Thus, the communication module can first be switched off during a parked phase, and only the receiver of the radio remote control has to be supplied permanently with electrical energy.
From WO 2007/028624 A1, it is known to provide a motion sensor in a motor vehicle and to switch a locating device of the motor vehicle between a sleep mode and an operating mode by means of the motion sensor. The locating device is activated as a function of a movement of the motor vehicle and it then sends location coordinates by text messages (SMS) via a mobile radio module.
From DE 103 47 839 A1, it is known, after the initiation of a parked phase, to first continue to operate a control unit in a follow-up mode for a certain time span, and to terminate a data transmission connection and deactivate a communication unit only after the expiration of the time span. As a result, the motor vehicle remains controllable in the follow-up mode by radio from outside the motor vehicle.
From DE 10 2006 024 634 B4, a method for wireless transmission of infotainment components between a vehicle network in a vehicle and a vehicle-external network is described. The vehicle network has a ready-to-receive state and a rest state, wherein, via a remote control of the vehicle, a switch is made from the rest state to the ready-to-receive state.
The methods for switching between a rest state and a ready-to-receive state known from the prior art are based on the continuous operation of a receiver which can generate a wake-up signal in the motor vehicle. For the case in which a motor vehicle remains parked for several weeks or months, that is the parked phase lasts that long, the continuous operation of a receiver also leads to a discharge of the vehicle battery, as a result of which the ability of the motor vehicle to restart can be impaired.
In DE 10 2007 046 944 A1, a pressurized air supply device with leakage analysis is described. A pressurized air supply module comprises a control unit with a wake-up circuit that is connected to an external timer. The timer issues wake-up signals to the control unit with a wake-up circuit, and, in the case of reception of the wake-up signal, the control unit carries out a measurement of a system pressure in the motor vehicle, while the ignition of the utility vehicle is switched off.
From DE 102 55 449 A1, a device for waking up a control unit in a motor vehicle is described. In the device, wake-up means in the rest state are not supplied with current, but instead they have their own dischargeable energy storage device.